Good evening fiends. How r u? Last time we talked about the adverbs of frequency and their uses and placement. Tonight, let's see how another kind of adverbs - called sentence adverbs - can be used. Look below:
He did not study hard. Consequently, he failed.
He is always unmindful to his duties in the office. Evidently, he has to suffer.
They met with a serious accident on the way. Fortunately, none got badly hurt.
We have been trying our best to solve the problem but nothing is coming out. Hopefully, our teacher is coming to help us.
In the above sentences, you can understand that Consequently, Evidently, Fortunately and Hopefully have come before a sentence to establish a link between the two sentences. They are also modifying the sentences that follow. That's why they are called sentence adverbs. 
Again look below:
You want to write a problem essay. Firstly, you have to describe the nature of the problem. Secondly, its cause. Thirdly, its effect and fourthly, remedies. Then, you can write a conclusion.
The same is in the case of Firstly, secondly, thirdly, fourthly and then. They connect sentences, both the preceding and the following.
That's all for now guys. Comment on this post if you will. Good night and sweet dreams.